Bio 1001 Exam 2 (Paul, LSU)

____ is the capacity to do work.

Energy

___________ is stored energy.

Potential Energy

____________ is the energy of movement.

Kinetic Energy

Describes the basic properties of energy.

The Laws of Thermodynamics

States that energy can be neither created nor destroyed.

The First Law of Thermodynamics

The _________ in an isolated system remains constant.

Total Energy

What is the first law of thermodynamics often called?

the law of conservation of energy

What usually happens when energy changes form?

The conversions usually result in the release of useful energy to the system.

States that when energy is converted from one form to another, the amount of useful energy decreases.

The Second Law of Thermodynamics

The tendency toward an increase in randomness, disorder, and low-level energy.

Entropy

A process that breaks and forms chemical bonds.

Chemical Reactions

What do chemical reactions do?

Convert reactants into products.

What makes a reaction endergonic?

If it requires a net input of energy.

The reactants have more energy than the products, energy is released.

Exergonic Reactions

Require a net input of energy. The products of a chemical reaction contain more energy than the reactants. An input of energy is required for the reaction to proceed.

Endergonic Reactions

Require activation energy to begin. Require some input of energy. The energy of activation provides the "push" to get started.

Chemical Reactions

What are the three steps in the cycle of enzyme-substrate interactions?

1. Substrate(s) enter the active site in a specific orientation.

2. Substrate(s) and active site change shape, promoting the reaction.

3. Product is released, enzyme is ready for new substrate(s).

What do living things use to maintain life?

Solar Energy

High-energy molecules that move energy within cells.

Energy-Carrier Molecules

The "energy currency" of living cells because it provides energy for a wide variety of endergonic reactions.

ATP

________ and _________ transport energy within cells.

ATP and Electron Carriers

What is ATP composed of?

Adenine, the sugar ribose, and three phosphate groups.

How can ATP be synthesized?

ATP can be synthesized from adenosine diphosphate and phosphate, using the energy released by exergonic reactions, such as glucose breakdown.

ATP can be broken down to ______ and _______ to provide energy for endergonic reactions.

ADP; Phosphate

Is ATP long-term or short-term energy storage?

short-term

In what form do electron carriers transport energy?

Electrons

What are common electron carriers?

NADH and FADH2

What do catalysts do?

They speed up chemical reactions by lowering activation energy. They are not consumed or permanently changed by the reactions they promote.

_______ are biological catalysts.

Enzymes

In living organisms, enzymes are usually _______.

Proteins

What do enzymes' structures allow them to do?

Catalyze specific reactions.

Because of its three-dimensional shape, an enzyme has a "pocket" that can do what?

Allows a specific reactant molecule, or substrate, to enter the active site.

Enzymes, like all catalysts, do what?

lower activation energy

Where do enzymes function?

Metabolic Pathways

Why are many metabolic pathways within a cell interconnected?

Different metabolic pathways often use the same molecules.

The sum of all chemical reactions within a cell.

Metabolism

How do cells regulate metabolic pathways.

By controlling enzyme synthesis and activity.

What does the rate of enzyme-catalyzed reactions depend on?

The concentration of enzymes and substrates.

How do cells regulate enzymes?

By regulating the genes that dictate the production of the enzyme.

Some enzymes are synthesized in inactive forms. When are these enzymes activated?

When the cell needs them.

A substance competes with the substrate for the active site of the enzyme.

Competitive Inhibition

A molecule binds to a site on the enzyme distinct from the active site.

Noncompetitive Inhibition

What are some things that influence enzyme activity?

Poisons, drugs, and environmental conditions.

Energy transferred to an object, usually causing the object to move.

Work

A form of potential energy that is stored in molecules and may be released during chemical reactions.

Chemical Energy

The energy of movement; includes light, heat, mechanical movement, and electricity.

Kinetic Energy

In thermodynamics, a hypothetical space where neither energy nor matter can enter or leave.

Isolated System

The principle of physics that states that within any isolated system, energy can be neither created nor destroyed, but can be converted from one form to another; also called the first law of thermodynamics.

Law of Conservation of Energy

The principle of physics that states that any change in an isolated system causes the quantity of concentrated, useful energy to decrease and the amount of randomness and disorder (entropy) to increase.

Second Law of Thermodynamics

An atom or molecule that is used up in a chemical reaction to form a product.

Reactant

An atom or molecule that is formed from reactants in a chemical reaction.

Product

Is glucose breakdown endergonic or exergonic? What about photosynthesis?

Glucose breakdown is exergonic; photosynthesis is endergonic

In a chemical reaction, the energy needed to force the electron shells of reactants together, prior to the formation of products.

Activation Energy

A pair of reactions, one exergonic and one endergonic, that are linked together such that the energy produced by the exergonic reaction provides the energy needed to drive the endergonic reaction.

Coupled Reaction

Can an enzyme catalyst make an endergonic reaction occur spontaneously at body temperature?

No, only exergonic reactions can occur spontaneously after the activation energy is overcome.

The region of an enzyme molecule that binds substrates and performs the catalytic function of the enzyme.

Active Site

The atoms or molecules that are the reactants for an enzyme-catalyzed chemical reaction.

Substrate

Having the secondary and/or tertiary structure of a protein disrupted, while leaving the amino acid sequence unchanged. Stops proteins from performing their biological functions.

Denatured

Which of the following is true?

A. Enzymes increase activation energy requirements.

B. Activation energy is required to initiate exergonic reactions.

C. Heat cannot supply activation energy

D. Stomach Acid inactivates pepsin

B. Activation energy is required to initiate exergonic reactions.

Which is NOT an example of an exergonic reaction?

A. photosynthesis

B. a nuclear reaction in the sun

C. ATP --> ADP +Pi

D. glucose breakdown

A. photosynthesis

Which of the following is true?

A. ATP is a long-term energy storage molecule

B. ATP can carry energy from one cell to another

C. ADP inhibits glucose breakdown in cells

D. ATP is produced by exergonic reactions

D. ATP is produced by exergonic reactions

Coupled reactions

A. are endergonic overall

B. both synthesize and break down ATP

C. are catalyzed by the same enzyme

D. end with reactants that contain more energy than their products

B. both synthesize and break down ATP

Enzymes

A. increase the rate of a reaction

B. are active across a wide range of temperatures and pH

C. are not very specific in the substrates they bind

D. are used up during catalysis

A. increase the rate of a reaction

According to the first law of thermodynamics, energy can be neither ______ nor _______. Energy occurs in two major forms: _________, the energy of movement, and ______, stored energy.

created; destroyed; kinetic, potential

According to the second law of thermodynamics, when energy changes forms some is always converted into _______ useful forms. This tendency is called ______.

less; entropy

Once started, some reactions release energy and are called _______ reactions. Others require a net input of energy and are called ___________ reactions. Which type of reaction will continue spontaneously once it starts? Which type of reaction allows the formation of complex biological molecules from simpler molecules?

exergonic; endergonic; exergonic; endergonic

The abbreviation ATP stands for ________________. The molecule is synthesized by cells from _______ and ________. This synthesis requires an input of ________, which is temporarily stored in ATP.

adenosine triphosphate; adenosine diphosphate; phosphate; energy

Enzymes are what type of biological molecule? Enzymes promote reactions in cells by acting as biological _______ that lower the _________. Each enzyme possesses a region called a(n) __________ that binds specific biological molecules.

proteins; catalysts; activation energy; active site

Some poisons and drugs act by __________ enzymes. When a drug is similar to the enzyme's substate, it acts as a(n) __________ inhibitor.

inhibiting; competitive

Explain why organisms do not violate the second law of thermodynamics. What is the ultimate energy source for most forms of life on Earth?

Life does not violate the second law of thermodynamics because Earth is not a closed system but instead is receiving a constant influx of energy from the sun, which is captured by organisms and used to maintain their organized complexity. The sun releases heat and undergoes a continuous increase in entropy.

Define metabolism, and explain how reactions can be coupled to one another.

Metabolism is the sum total of all chemical reactions in a cell. Reactions are coupled so that one reaction releases energy (exergonic) to drive another reaction (endergonic). Energy-carrier molecules, particularly ATP, transfer chemical energy from exergonic to endergonic reactions. In every conversion, some energy is lost as heat.

What is activation energy? How do catalysts affect activation energy? How do catalysts affect the reaction rate?

Activation energy is an initial input of energy required to start a chemical reaction. Catalysts reduce the amount of activation energy required to start a reaction, which results in the reaction proceeding at a much faster rate.

Compare the mechanisms of competitive and noncompetitive inhibition of enzymes.

In competitive inhibition, a substance that is not the enzyme's normal substrate binds to the active site of the enzyme, competing with the substrate for the active site. In noncompetitive inhibition, a molecule binds to a noncompetitive inhibitor site on the enzyme that is distinct from the active site. As a result, the enzyme's active site is distorted, making it less able to catalyze the reaction.

Describe the structure and function of enzymes. How is enzyme activity regulated?

Enzymes are nearly always proteins with complex three-dimensional shapes that bind to specific substrates. Enzyme activity is regulated in three ways:

1. A cell may regulate how much of an enzyme it contains by turning genes on or off.

2. A cell may synthesize an enzyme in an inactive form that is activated only when necessary.

3. A cell can temporarily activate or inhibit enzymes through allosteric regulation.

When electrical energy is used to turn on a light bulb, the conversion from electrical energy to light energy is not 100% efficient. This loss of usable energy can be explained by _____________.

The Second Law of Thermodynamics

Noncompetitive inhibition of enzymes (such as with potassium cyanide) relates to the ____________________.

binding of a molecule at a site other than the active site, which in turn changes the overall structure of the active site to prevent the substrate from binding.

If all matter tends toward increasing randomness and disorder, how can life exist on Earth?

There is a constant input of energy from the sun.

The most important factor about the active site of a protein-based enzyme is its ______.

shape

Potential energy represents __________.

stored energy

If the products of a reaction produced inside a cell have more energy than the reactants, then we say this is likely to be a(n) ______________.

endergonic reaction

Why do most reactions occur more rapidly at higher temperatures?

Molecules move more rapidly, allowing for more frequent and forceful collisions between electron shells.

The speed of a reaction is determined mostly by its ____________.

activation energy

Electron carrier molecules that transport energy include _______________.

NADH and FADH2

Which of the following situations illustrated the coupling of exergonic to endergonic reactions in cells?

A. the diffusion of oxygen into the cell and carbon dioxide out of the cell

B. the breakdown of glucose, producing ATP

C. absorption of water by a root cell

D. the production of a protein by dehydration synthesis

B. the breakdown of glucose, producing ATP

Why is ATP so important to cells?

ATP hydrolysis is exergonic and can be coupled to endergonic reactions.

How is ATP used in energy metabolism?

ATP synthesis is coupled to an exergonic reaction, the breakdown of glucose.

Which of the following statements is correct about how enzymes work?

A. The product(s) enter the enzyme active site in specific orientations.

B. The substrate(s) enter an alternative binding site other than the active site on the enzyme.

C. Enzymes catalyze specific chemical reactions because the shape of their active site allows only certain substrate molecules to enter.

D. Enzymes can function over a wide range of temperatures.

C. Enzymes catalyze specific chemical reactions because the shape of their active site allows only certain substrate molecules to enter

Energetic electrons produced by exergonic reactions, such as those involved in the breakdown of glucose, are then captured by electron carriers such as?

The nucleotide-based molecules NADH and FADH2

The main function of enzymes in the cell is to lower the ______________ of the reaction.

overall energy

The most important reason a particular enzyme can function only within certain limits of temperature, salt concentration, and pH is that...

changes in temperature, salt concentration, and pH change the shape of an enzyme.

The process by which solar energy is captured and stored as chemical energy in the bonds of organic molecule.

Photosynthesis

Where does photosynthesis occur?

Algae, certain types of bacteria, and land plants.

________ and _______ are adaptations for photosynthesis.

Chloroplasts and leaves

Photosynthesis consists of the _______ reactions and the ________ cycle.

light; Calvin

What happens during light reactions during photosynthesis?

Chlorophyll captures light energy and converts it into the energy-carrier molecules ATP and NADPH. Oxygen is released as a byproduct.

What happens during the Calvin cycle?

Enzymes in the stroma synthesize sugars. This process uses CO2 from the air and ATP and NADPH from the light reactions as an energy source.

How is light captured in chloroplasts?

by pigments

What is light composed of?

Individual packets of energy called photons.

Short-wavelength photons have ______ energy; long-wavelength photons have _____ energy.

high; low

What is visible light composed of?

Wavelengths of light that are energetic enough to power reactions but not damage cells.